Radio transmission differs most significantly from wired signaling in its (almost universal) omnidirectionality. Of course, decoupling communication from the localized infrastructure of cables is precisely what drives wireless networks and which make these an economic success story. However, the absence of a physical other end of the wire is one factor which makes the management of wireless networks difficult. A network manager typically cannot physically locate a trouble-spot or other transmission source in the network.
Wireless networks offer advantageous solutions for allowing communication between two or more computers or other electronic devices (for example, PDAs, tracking devices, inventory devices and other so-called handheld devices) using a networking protocol without requiring a physical link between computers or other networked devices. Two examples of a wireless network protocol are the so-called Wi-Fi and WiMAX standards formally known as the 802.11 and 802.16 standards adopted by the Institute of Electrical and Electronics Engineers (IEEE). The IEEE and other organizations have adopted, proposed, discussed, and debated various other wireless networking specifications, such as other in the 802.11 family including the 802.11, 802.11a, and 802.11g standards. Furthermore, there are many other approaches to wireless networking which have not been adopted or implemented as formal standards, or which were implemented or adopted at one time but have now been superseded. In theory, there are a virtually limitless number of configurations, protocols, and standards for wireless networks.
Wireless networks present a number of network management, identification, location, and security challenges which can benefit from the ability to locate sources interacting with a wireless network. Many problems in wireless networking stem from the fact that users and their equipment are mobile within a given network range and from time to time enter and exit wireless networks. Thus, unlike devices attached to wired networks, a user's location is often unknown and difficult, if not impossible, to determine using current technology. This makes traditional network management and security approaches ineffective. Thus, at present, Wi-Fi has become nearly ubiquitous, yet the managers of Wi-Fi networks lacks adequate apparatuses, systems, and methods for effective, let alone optimal, management.
Wi-Fi operates in an unlicensed band, shared with industrial equipment and other non-communicating devices. Furthermore, the applicable Federal Communications Commission's rules (FCC Part 15) do not require any coordination among Wi-Fi users or uses. Unlike, for example, cell phones, Wi-Fi devices are often configurable by the end user, which allows anyone to set up ad-hoc networking structures, even in disregard of any existing institutional network regulations, or, for that matter, the intention, wishes, rules, or regulation of anyone else. Naturally, this opens the door to accidental and intentional disruption of communication and myriad other problems and obstacles to optimal wireless network operation.
In addition, radio communication is by its nature spatially distributed. Mere detection of a network ID (such as an IP address) in a wireless network does not reveal the location of an interlocutor, an authorized user, or a user of undetermined status which makes it difficult for a network manager to even physically locate a user or a possible trouble spot in the network.
Also, a consequence of the omnidirectional wireless transmission is that the signal strength generally drops off very rapidly with distance. The intended receiver typically receives a minuscule fraction of the energy of the transmission, and considerable engineering effort goes into recovering the signal from that low energy level. Virtually all of the transmitter's power is wasted, and worse the message to the intended receiver is simultaneously an interference which prevents communication between all other network agents in that band, within the receiving range.
The problem of radio signal drop-off can be alleviated with high-gain dish antennas, but the technique applies only to communication between fixed points, and is scarcely usable in the light-weight, ad-hoc, mobile world of the Wi-Fi. Relatively crude hand-held yagi direction finders and power meters could be used as Wi-Fi management tools, but there is little by way of versatile Wi-Fi management tools operating in the physical layer. For example, the single physical-layer diagnostic tool that is commonly supplied with Wi-Fi devices today, reporting of the signal strength, is crude and inaccurate.
An example illustrating the need for radiolocation of clients in a wireless network is as follows. Currently Internet Protocol or IP addresses are assigned by network servers. A common difficulty with wireless networks is that multiple clients (e.g., devices that can communicate wirelessly) may be assigned the same IP address. When two clients are communicating with a server using the same IP address, this situation results in one client being disconnected from the network.
While several approaches to locating sources in a wireless network have been attempted, there is still a need for an efficient, accurate and reliable solution. One existing approach relies on algorithmic analysis of the traffic to and from multiple network agents. For example, software systems can be “trained” to correlate the location of a source with received signal strengths (RSS) at multiple receivers in a known environment, such as an office suite. This approach requires dense coverage with receivers, and the system would need to be specifically trained for the environment at each deployment site. If the physical environment were to change (for example, if a new wall were built or a new user were to enter the system), the system would need to be re-trained.
Another known approach involves use of techniques similar to those of Global Positioning Systems (GPS). This approach determines the distance of a receiver from multiple network nodes, by measuring the signal times-of-arrival (TOAs). This approach is problematic in the wireless network context, since, unlike a GPS system, the distances in the wireless network applications are much smaller (and the transmission times much shorter). Thus, there could be significant technical difficulties in accurately measuring such short time intervals in wireless networks.
Another known approach includes measuring the slightly different times at which a single wavefront arrives at multiple elements of a compound antenna. These elements could be in a fixed spatial arrangement, and thus can be referred to as a phased array. This method can yield the angular direction of the incoming signal, using techniques similar to those of phased-array radars and large-scale radio astronomy. To an even greater degree than TOA, phased arrays would require accurate measurements of very short time intervals (on the order of pico-seconds, for realistic Wi-Fi receiver sizes). Thus, there would be significant technical difficulties in accurately measuring such short time intervals in a wireless network.
As a result, wireless networks are as a rule poorly managed, and network administrators find it difficult to provide a consistent quality of service to the users. Yet for these very same reasons, Wi-Fi is a commercial success, with sales volumes sufficient to bring the cost of individual devices down into the range of tens of dollars. Low cost of the equipment, absence of physical infrastructure (wiring), and the do-it-yourself unregulated nature of the communication, allow easy entry to new users. Hospitals, delivery services, police and others all make use of Wi-Fi as an integral part of their business and operations process. Thus, there is a clear benefit to developing better management tools, processes and knowledge in the Wi-Fi arena.